FOR the first six years that he knew her, Justin Feinstein could find nothing to scare the woman known as “SM”. It wasn’t for lack of trying. He showed her films like The Blair Witch Project, Arachnophobia, The Shining and Silence of the Lambs, but none elicited even a hint of fear. He then took her to an exotic pet store where, without provocation, she approached a terrarium of snakes and reached in to hold one. She even touched its flicking tongue and declared, “This is so cool!” SM approached the animals with so little caution that a shop assistant had to intervene to stop her petting a tarantula.

Next, Feinstein took her to Waverly Hills Sanatorium in Louisville, Kentucky – a haunted house tourist attraction billed as “one of the scariest places on Earth”. Once again, nothing rattled her. While others taking the tour startled or screamed at the strange noises, creepy music and eerie scenes featuring actors dressed as murderers, monsters and ghosts, SM smiled and laughed. In an ironic twist, she managed to frighten one of the “monsters” when she reached out to touch its head – just to find out what it felt like, she later explained.

Feinstein’s mission to scare SM might sound like the pranks of a mischievous sibling, but it has a serious purpose. He is a clinical neuropsychologist at the California Institute of Technology in Pasadena, and he believes that studying SM, and a handful of people with a similar lack of fear, could pave the way for a better understanding of how …